Can't access "High Resolution" option in Physics Properties
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The "High Resolution" option no longer exists.

In recent updates to Blender, the fluid simulation tools (which is what handles liquids, smoke, fire, and anything else fluid) have been completely replaced. This happened in Blender 2.82. The new system uses something called MantaFlow, so any tutorials that use 2.82 or later, or specifically say MantaFlow, should be more relevant.

If you want to continue with that tutorial, I would just manually increase the resolution, which is all that the old "High Resolution" option did I believe.